Visible light signatures exist on nearly all weapons to some degree and are problematic for a number of reasons including not the least of which is indicating the gun position and also possibly the orientation of the weapon to opposing forces upon firing. The intensity of the visible light signature tends to vary from weapon to weapon, but generally speaking the problem is compounded when firing automatic weapons due to an increase in operating temperature of the barrel as well as an increase in physical wear and material degradation of the bore in the gun barrel. Periodically firing tracer rounds to aid in target acquisition, which is also a common practice, also tends to catalyze the onset of flash. There are many situations where visible flash is incompatible with military mission objectives, and as a result muzzle flash suppressors are often used to reduce the visible light signature on small and medium caliber weapons.
The United States Army has been studying this problem and has developed designs for a number of flash suppressors. The US Army Material Command has published a coordinated series of engineering design handbooks containing basic information and development of Army material and systems. In May 1968, a handbook as one of a series on guns entitled Muzzle Devices presents information on the fundamental operating principles and design of muzzle devices. These muzzle devices include muzzle brakes, blast deflectors, and flash suppressors. In the preface of this publication, one particular statement, which is still pertinent and highly appropriate today states that the effort to improve all muzzle devices continues, and this effort is being augmented by studies on human behavior when exposed to the phenomena created at the gun muzzle.
Flash suppressors have been recognized as a significant problem for betraying gun position since World War I. The search for a flash eliminator or an effective flash suppressor became almost as intense as the search for a higher performing gun although it has lagged since flash suppressor behavior was not fully understood and continues to be the subject of faulty explanations of their theory of operation. In Chapter 5 of the handbook entitled Flash Suppressors, the bar type, which is now often referred to as the open-prong type, or the open-cage type, for smaller caliber weapons, is considered including computerized analysis of the modifications to gas flow upon firing of the weapon. While the bar type is just one example, a variety of muzzle flash suppression devices have existed for some time yet none of them completely eliminate flash in all cases.
The combination of reduced length of the M240B lightweight short barrel along with its use on the fully automatic M240B medium machine gun involving sustained gunfire presents a significant challenge to the effectiveness of most traditional flash suppressor designs in terms of reducing visible light signature. Flash reduction for the family of M240 machine guns also becomes especially important when considering the detrimental effects of visible light during operations conducted in black out mode using night vision equipment. One of the most effective muzzle flash suppressors tested to date on the M240B lightweight short barrel is an open-prong design with angled flutes in the direction of rifling. This flash suppressor is similar to the design disclosed in U.S. Pat. No. 5,596,161 of Sonja Sommers that is available from SMITH ENTERPRISE, INC.